In certain industries and/or applications, separating one material from a second material is often desired and/or required. Further, the separation of solids and fluids is generally known in a variety of industries and/or applications. For example, industrial separators use screens to separate solids and/or fluids as desired. Also, the mining industry has many applications in which solids may be separated from fluids to extract a desired ore and/or metal during mining processes. Further, on-shore and/or off-shore drilling applications use various methods and/or equipment to separate solids from fluids in drilling processes.
Conventional vibratory screen apparatus for sifting material generally utilize screens of either hook strip or pretensioned design. Hook strip screens generally have a single layer or multiple layers of mesh bonded together. The screens may be tensioned after the screens have been mounted in the basket of the vibratory screen apparatus. Two opposed ends of the screen are fitted with a turn back element to form a hook strip. The hook strip may be hooked around a tension rail which may be attached to the side wall of the basket. Typically, a tension bolt may be used. However, other loading means to apply tensioning and securing forces may be employed. Tightening the tension bolt may move the tension rail outwardly towards the walls of the basket to apply tension to the screen.
Hook strip screens may be pretensioned prior to mounting in the basket by attachment of the screen mesh element to an apertured support plate, typically by means of an adhesive. A screen having a plurality of mesh layers may be pretensioned. In some designs, layers of fused mesh may be corrugated prior to mounting to an apertured support plate and the hooks applied thereafter to the mesh-plate combination.
Hook strip screens have a number of disadvantages including the complex and time consuming mounting of the screen members in the basket which results in significant downtime of the vibratory screen apparatus and requires the use of multiple parts. Attaining the correct screen tension for the sieved material also involves intricate fine tuning. The screens may be easily damaged if too much force is applied when tightening the bolts or loading means to tension the screens. A further disadvantage is the relatively poor sealing between the screen and basket. The metal on metal seal often results in leakage. Unscreened material may pass through gaps between the screen and the basket and may mix with already screened material below the mesh screen. Attempts to overcome the poor seal by placing rubber strips and/or gaskets at the metal/metal interfaces require intricate and time-consuming fitting. The strips and/or gaskets frequently work loose during vibration and become lost or lodged in the vibratory machine which obstructs and/or damages the machinery. In addition, applying tension to the screen when tightening the tension bolt adds undesirable stresses to the machine frame.
Pretensioned screens generally have one or more layers of mesh permanently bonded under tension onto a generally rigid steel and/or plastics material apertured plate support frame. The mesh screen may be flat or crowned. The screen and frame are inserted into the basket as a unit which requires no adjustment to the tension of the screen. The screen and frame are normally secured in the machine by clamps from above and/or below. The clamps may be hydraulic pistons, inflatable clamping bags, bolts, tapered elements and/or the like.
Conventional pretensioned screen units with integral support frames have significant disadvantages. For example, conventional pretensioned screens may be bulky, heavy and difficult to handle, transport and store. Typically, the design may be complex, and the frames may be expensive to construct. Plastic injection molding is commonly used which is an inflexible method of construction. The frames utilize large amounts of material which require disposal when the screen units are replaced. The disposal is inconvenient, expensive and negatively impacts the environment.
Over the life of the screen, the particles cause wear on the wire mesh. Damage causes a breach in the mesh. As a result, that area of the mesh allows larger particles to pass through than desired. After the damage occurs, the screen must be replaced or repaired.
Thus, many conventional screens may be large and cumbersome to handle during transportation, installation and/or removal. Manipulating the screens is difficult for a single user. The large screens may also be rigid which increases the difficulty in removing the screen from the separator. Also, the rigid screens are difficult to transport and/or store. In certain situations in which the available space surrounding the separator is limited, maneuvering the screens for installation and/or replacement is challenging.